This invention relates generally to fluid dispensing systems, and more particularly to systems for mixing two fluids together in prescribed relative proportions and to systems for supplying a fluid at a prescribed average flow rate.
Systems of this type are of particular use as post-mix soft drink dispensers for mixing together and dispensing carbonated water and flavored soft drink syrup in a prescribed mix ratio. These systems typically inject the water and syrup simultaneously into a mixing chamber, where they are mixed together and then dispensed through a nozzle into a drinking cup. The two fluids are normally supplied for coextensive time durations, and the mix ratio is typically controlled using manually-adjustable metering valves.
Although the typical post-mix dispensing systems described above operate satisfactorily in most situations, variations in the pressure of the carbonated water can sometimes cause corresponding variations in the relative proportions of the dispensed water and syrup. Some systems have overcome this problem by including relatively complex and expensive structures for regulating the water pressure. Other systems have sought to maintain a fixed mix ratio by controllably adjusting a syrup valve in accordance with the water's pressure. It is believed, however, that these systems are unduly sensitive to pressure variations. Also, many of these systems are believed to be unduly complex and to require substantial manual adjustments when changing from one type of syrup to another.
It should therefore be appreciated that there is still a need for a system for mixing together and dispensing two fluids with a prescribed mix ratio, which is substantially insensitive to variations in fluid pressure and which can be conveniently and reliably modified to provide different mix ratios. It should also be appreciated that there is still a need for an inexpensive yet reliable system for supplying a fluid at a prescribed average flow rate, regardless of its initial pressure. The present invention fulfills these needs.